Numerous embodiments of in-glass antennas in a monolithic or laminated embodiment are known, in which embodiments antenna structures are placed directly on the glazed surface or within the lamination of the sheets. The present invention, however, by way of preferred application, relates to antennas to be mounted separately on the glass sheet.
Nonetheless, it must be understood that the present invention can be used not only on motor vehicle laminated glass sheets but also on the glass sheets used in buildings. It is not a matter of fixing the glass sheet itself onto a structure but of using the glass sheet, itself equipped with a through-hole, as a support for an object fixed to it.
It is also known practice for objects such as rear-view mirrors, for example (DE 35 09 531 C1), antennas and/or sensors to be fixed to glass sheets by bonding them onto one of the main surfaces thereof, without there being a need for any orifice in order to do so.
Document DE 30 20 253 A1 describes a fixing of an antenna (not of this kind) into a motor vehicle monolithic windshield. This windshield has a hole into which an antenna holder element is introduced removably. The holder element has a stem part that fits into the hole and a neck, which is larger than the diameter of the hole. This neck presses against one of the faces on the surface of the windshield via an intermediate layer that acts as a seal. The holder element is fixed by a screw screwed from the other side of the windshield into the stem part thereof via a back support piece, the back support part also pressing via an intermediate layer that acts as a seal against the opposite surface face of the windshield to the holder element. It at the same time acts as a base for an interior rear-view mirror.
Document DE 10 2004 011 662 A1 discloses a fixing for an antenna on a sunroof of a motor vehicle. The (monolithic) sunroof is provided, at the point where the antenna is mounted, with an orifice into which the antenna is introduced. At the same point, a metal plate with a corresponding orifice on the underside of the sunroof has, however, to be provided out of functional necessity, as this plate has to provide the antenna with a ground potential. The antenna is introduced into the orifices and screwed, a sealing gasket between the antenna body and the glass being positioned on the external glazed surface.
This teaching can be put only to limited use in respect of an antenna actually properly introduced into a glass sheet, and it does not cover laminated glass sheets even though these are normally used on motor vehicle sunroofs and windshields.
Document DE 43 11 442 C1 describes a method for screw-fastening a fixing or retaining element onto a corresponding laminated glass sheet, whereby the retaining element is introduced into an orifice passing through the two sheets of lamination. The known method addresses the problem that the layer between the laminations or layer of adhesive must not be loaded with the pressure involved in the tightening of a screw because it could then ultimately let go. The two sheets are therefore provided with orifices of different sizes, which are positioned eccentrically with respect to one another in the lamination. In order to relieve the load on the adhesive layer of the lamination, the space between the fixing parts introduced into this orifice of a smaller size and the walls of the hole is filled with a thermosetting plastic which is supposed to bear the forces of tensioning of the screw fastening. By virtue of the eccentricity of the two holes, the retaining element is also protected against torsion. According to that publication, the two parts of the fixing device also press against the exterior surfaces of the two rigid sheets of the lamination.
Document DE 44 04 165 C1 describes a method for increasing the compression stresses in the region of an orifice in a monolithic sheet that is prestressed in its entirety, whereby, during the contact prestressing process, a cooling means is also brought into the orifice. In this way, the region of the walls of the hole is prestressed in a targeted fashion using a thermal process.